Patent GB-727964-A (GB)
Title: Improvements in or relating to metering and regulating systems
Inventor: BURNUP THOMAS ELLIOTT
IPC: G05B1/02
Filed: 1950-09-20
Abstract: 727,964. Potentiometric voltage and current measurement. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Sept. 10, 1951 [Sept. 20, 1950], No. 23041/50. Class 37. [Also in Group XL (b)] In a metering or regulating system of the kind in which current or voltage dependent on the variable to which the system is responsive produces a voltage drop or current flow comparable witli a reference voltage or current; the dependent current or voltage is applied to an adjustable resistance calibrated in discrete values of the variable to give the predetermined same value of voltage drop or current flow at all resistance settings whenever a value of the variable corresponds to the appropriate calibrated resistance setting and a reference source of voltage or current corresponding to the predetermined output value, there being provided a comparator circuit responsive to the reference source and the output of the adjustable resistance, to produce an error signal proportional to the difference in value between the actual output and the reference source. Fig. 3 shows control apparatus for an atomic pile in which an ionisation chamber (not shown) containing e.g. boron trifluoride gas passes current proportional to neutron flux and thus to the pile power level through two parallel banks 7, 9 of equal resistors, the number of each bank inserted in parallel being controlled by drum switches 8, 10 so that the total resistance in each bank is adjustable in decade steps to determine the required power level of the pile. The resultant voltage drop is connected to a meter 13 in opposition to a standard voltage derived from a potentiometer 12 across a voltage source, and the meter deflection controls a rebalancing servo-system 14 adjusting the potentiometer until the standard voltage and the power measurement voltage balance and the meter is undeflected. The servo-system may operate an indicator-recorder to show the percentage deviation of the pile power from the desired level set up on the switchable resistor banks 7, 9, and may also regulate the position of controlling rods within the pile. In a modification (Fig. 4) the two sets of switchable decade resistors 7, 9 are connected in parallel with a fixed resistor R2 in series with a variable resistor R1 giving a resistance variation of ¢ r to r (corresponding to a power range of P min. to 2 P min.), where r is the value of a single decade resistor, for vernier control. The voltage drop across the variable resistor bank is compared with a fixed reference voltage V in a D.C. amplifier AMP whose output may be utilised to operate an indicator or control the pile power. A fixed current i equal to that representing the minimum allowable pile power P min. is introduced into the ionisation chamber circuit so that the effective vernier range is O to P min. The ionisation chamber is replaceable by a " neutron thermometer," i.e. a thermocouple heated by neutron flux and giving a variable voltage dependent thereon, in which case the parallel decade resistors are replaced by series switchable decade resistors and the current obtained therethrough is similarly compared with a constant reference current to indicate or control the pile power.